A hydrogel contains water as its medium and is therefore useful as a highly biocompatible gel. This gives a hydrogel a wide range of applications, for example, in the fields including daily necessities such as disposable diapers, cosmetics, and fragrances.
A conventional hydrogel is a polymer gel that is obtained from polymer chains crosslinked to form a three-dimensional network structure which is then bonded to a medium such as water through non-covalent bonds to cause swelling. The physical properties and the applications of such a polymer gel have been researched in large number on natural polymer gels containing a polysaccharide such as agarose and a protein and on synthetic polymer gels such as a acrylamide gel obtained by forming crosslinks between polymer chains through chemical covalent bonds.
Besides these gels that contain polymer compounds, a hydrogel that is obtained by self-assembling of an organic compound having relatively low molecular weight has been developed and extensively studied in recent years.
Most of the low-molecular gelators that have already been developed are amphiphilic compounds having a combination of a hydrophobic moiety that is a long-chain alkyl group and a hydrophilic moiety, and examples of these gelators include one having an amino acid [Non-patent Document 1], one having a peptide [Patent Documents 1 and 2], one having a saccharide [Non-patent Documents 2 and 3], and one having a polyol [Non-patent Document 4], as the hydrophilic moiety. In addition, a low-molecular gelator that utilizes the characteristics of a peptide consisting of valine to readily form a β-sheet structure has been developed [Non-patent Document 5].
Using the low-molecular hydrogelators described above, a hydrogel can be formed by stirring the hydrogelators and water as a medium with heating at the temperature of about 100° C. so that the hydrogelators are dissolved and dispersed in water, and by leaving the resulting solution still standing at room temperature.